Phenolic content and heritability of resistance in four hybrid populations of Theobroma cacao L. after leaves inoculation with Phytophthora megakarya Bras. et Grif

Cocoa is cultivated in Cameroon for its broad beans. The commercialization of cocoa seeds constitutes a major source of income to farmers. Nevertheless, cacao black pod disease caused by Phytophthora megakarya is responsible of about 80% of cocoa production loss in Cameroon without any protection method. To assess the resistance of cocoa plants against this pathogen, necrotic lesions and phenolic content were conducted on 3 clones (SNK16, ICS40, Sca12) and their progenies (families F40, F12, F20 and F25) after leaves inoculation. The existence of strong hybrid vigour has been shown. All hybrid genotypes manifested a positive heterosis effect for this symptom suggesting the existence of hybrid vigour. Some hybrids like F40.6, F40.7, F40.8, F40.9, F40.10, F12.10, F12.15, F20.7, F20.10, F25.2, F25.5 and F25.7 were characterized by localized lesions. A negative correlation between the size of necrotic lesions and the total phenolic compound was demonstrated. Three genotypes of the F40 family (F40.8, F40.9 and F40.13), one of the F12 (F12.15) and two of the F25 (F25.2 and F25.8) had small lesions and high concentrations of phenols. These six genotypes can be considered as elite clones with high tolerance to P. megakarya. The values of the heritability of lesion size and the total phenolic content in offsprings don’t show the maternal effect.Keywords: Cocoa, Phytophthora megakarya, heterosis, heritability, necrosis, phenol

Grain morphological characterization and protein content of sixty-eight local rice (Oryza sativa L) cultivars from Cameroon

Rice (Oryza sativa L.) cultivated in Cameroon is appreciated by consumers for its nutritive quality and good taste. Diversity of 68 local rice cultivars was investigated via grain morphology and protein content characterization. The size and shape of grains were determined and used with yield parameters to classify the cultivars and perform Principal Component Analysis (PCA). Total protein content and glutelin content of eight selected cultivars (CMRGNd, CMRGDn, CMRGTï, CMRTBa, CMRDWb, CMRDTc3, CMRDTx5 and CMRDTx6) were evaluated by Bradford assay and correlation analysis of all the parameters studied was performed. Long size grains (42) were predominant over extra-long (16), medium (9) and short (1) grains. Slender shaped grains (36) were distinguished as well as medium (28) and bold (4) grains. The 68 cultivars were grouped into four clusters independent of their origins. PCA revealed three principal components accounting for 74.4% of total variation. Highest total protein content was observed in CMRGNd (14.3%) and highest glutelin content in CMRGDn (10.1 mgEqvBSA/g DW). Pearson correlation of the different variables revealed no significant correlation between total protein and glutelin contents with the agro-morphological parameters evaluated in this study. This suggests that none of these parameters could be descriptor for protein content. Positive correlation between grain length and yield (r = 0.7) suggests grain length as yield descriptor

Grain morphological characterization and protein content of sixty-eight local rice (Oryza sativa L) cultivars from Cameroon

Rice (Oryza sativa L.) cultivated in Cameroon is appreciated by consumers for its nutritive quality and good taste. Diversity of 68 local rice cultivars was investigated via grain morphology and protein content characterization. The size and shape of grains were determined and used with yield parameters to classify the cultivars and perform Principal Component Analysis (PCA). Total protein content and glutelin content of eight selected cultivars (CMRGNd, CMRGDn, CMRGTï, CMRTBa, CMRDWb, CMRDTc3, CMRDTx5 and CMRDTx6) were evaluated by Bradford assay and correlation analysis of all the parameters studied was performed. Long size grains (42) were predominant over extra-long (16), medium (9) and short (1) grains. Slender shaped grains (36) were distinguished as well as medium (28) and bold (4) grains. The 68 cultivars were grouped into four clusters independent of their origins. PCA revealed three principal components accounting for 74.4% of total variation. Highest total protein content was observed in CMRGNd (14.3%) and highest glutelin content in CMRGDn (10.1 mgEqvBSA/g DW). Pearson correlation of the different variables revealed no significant correlation between total protein and glutelin contents with the agro-morphological parameters evaluated in this study. This suggests that none of these parameters could be descriptor for protein content. Positive correlation between grain length and yield (r = 0.7) suggests grain length as yield descriptor

Field Performance of Xanthosoma sagittifolium L. Schott Minitubers Grown Under the Influence of Poultry Manure and NPK Fertilizers: Changes in Content of Some Secondary Metabolites

The response of white and red cultivar (cv) cocoyam (Xanthosoma sagittifolium (L.) Schott) minituber seeds to different rates of poultry manure (PM) and NPK (20:10:10) fertilizer was studied under field conditions in the 2017 cropping season on an experimental farm at Ngog Bibega, Mbankomo Sub-division, (outskirsts of Yaounde) Centre region, Cameroon. Treatment combinations comprising of three rates each of poultry manure (0, 20 and 30t ha-1) and NPK fertilizer (0, 120 and 150 kg ha-1) were factorized and fitted into a randomized complete block design with three replicates. Physico-chemical analysis of all treatment plots revealed clay loam textures and poultry manure treatment plots significantly (P<0.05) increased soil pH, organic content, total carbon and cation exchange capacity while NPK treatments significantly (p<0.05) increased available phosphorus compared to the control treatments. Poultry manure(30t ha-1) treatments significantly (P<0.05) enhanced plant height, leaf number and leaf area in both cultivars after 6 months of growth as compared to all other treatments. Under the same treatments of poultry manure (30t ha-1) the white cultivar plants recorded the most significant mean yield parameters after 9 months of growth. The average tuber number per plant (8), tuber weight (250g), tuber length (14cm) and tuber girth (18.5cm) compared to the red cultivar average yield parameters: tuber number per plant (5.7), tuber weight (124.7g), tuber length (8cm) and tuber girth (14.5cm). Biochemically the application of various treatments of poultry manure and NPK fertilizers significantly (P<0.05) influenced the changes observed in the secondary metabolites studied. Two months after planting, NPK (150kg ha-1) treatments showed the most significant phenolic content (1.22±0.13mg eq catechin.g-1 FW) and flavonoid content (1.08±0.16mg g-1 FW) in white cv cocoyam plants. After 6 months of growth, the poultry manure (30t ha-1) treatments recorded the most significant protein content (5.04±0.38mg eq BSA.g-1 FW) and peroxidase activity (4.89±1.36 UE min-1) in white cv cocoyam plants while red cv cocoyam plants had the most significant glucanase activity (9.33±1.17 mg eq glucose g-1 FW). NPK (150kg ha-1) treatments in white cv cocoyam plants recorded the most significant polyphenol oxidase activity (4.99±0.10 in D330 nm-1 min-1 UE-1 g-1 FW) 6 months after planting. Keywords: Xanthosoma sagittifolium L. Schott; Minitubers; cation exchange capacity; Poultry manure; NPK fertilizers; yield parameters and secondary metabolites. DOI: 10.7176/JBAH/9-20-05 Publication date:October 31st 201

Genome-Wide Transcriptional Analysis and Functional Validation Linked a Cluster of Epsilon Glutathione S-Transferases with Insecticide Resistance in the Major Malaria Vector Anopheles funestus across Africa

Resistance is threatening the effectiveness of insecticide-based interventions in use for malaria control. Pinpointing genes associated with resistance is crucial for evidence-based resistance management targeting the major malaria vectors. Here, a combination of RNA-seq based genome-wide transcriptional analysis and RNA-silencing in vivo functional validation were used to identify key insecticide resistance genes associated with DDT and DDT/permethrin cross-resistance across Africa. A cluster of glutathione-S-transferase from epsilon group were found to be overexpressed in resistant populations of Anopheles funestus across Africa including GSTe1 [Cameroon (fold change, FC: 2.54), Ghana (4.20), Malawi (2.51)], GSTe2 [Cameroon (4.47), Ghana (7.52), Malawi (2.13)], GSTe3 [Cameroon (2.49), Uganda (2.60)], GSTe4 in Ghana (3.47), GSTe5 [Ghana (2.94), Malawi (2.26)], GSTe6 [Cameroun (3.0), Ghana (3.11), Malawi (3.07), Uganda (3.78)] and GSTe7 (2.39) in Ghana. Validation of GSTe genes expression profiles by qPCR confirmed that the genes are differentially expressed across Africa with a greater overexpression in DDT-resistant mosquitoes. RNAi-based knock-down analyses supported that five GSTe genes are playing a major role in resistance to pyrethroids (permethrin and deltamethrin) and DDT in An. funestus, with a significant recovery of susceptibility observed when GSTe2, 3, 4, 5 and GSTe6 were silenced. These findings established that GSTe3, 4, 5 and 6 contribute to DDT resistance and should be further characterized to identify their specific genetic variants, to help design DNA-based diagnostic assays, as previously done for the 119F-GSTe2 mutation. This study highlights the role of GSTes in the development of resistance to insecticides in malaria vectors and calls for actions to mitigate this resistance

Assessing relationship between phenolic compounds and resistance tPhytophthora megakarya using two cocoa (Theobroma cacao) families

Black pod disease is an important fungal infection in cocoa (Theobroma cacao L.) which causes high production losses. In Cameroon, these losses reached 80% of cocoa production depending on ecological zones. In order to contribute to the efficiency of selection methods used in resistance or tolerance to black pod disease with the aim of improving on cocoa farming, the content of phenolic compounds was analyzed on the genotypes of two hybrid families (F79:♀T79/467x♂SNK13 and F13:♀SNK13x♂T79/467) of cocoa which are different in productivity and vulnerability to black pod disease. After artificial inoculation of the pods by mycelium of Phytophthora megakarya, the content of the phenolic compounds significantly increased in all genotypes of the two families. The heterosis effect of each family revealed a higher variability within both families. These results alike showed that productive and tolerant genotypes (F1307, 1314, F7902 and F7928) have a high phenols content and positive heterosis meanwhile the less tolerant and productive genotypes (F1321, F1326, F7904 and F7911) have a weak content and negative heterosisKeywords: Cocoa, disease, tolerance, heterosis effect, phenolic compounds, hybrid progeniesAfrican Journal of Biotechnology Vol 13(29) 2956-296

VARIATION OF b-1,3-GLUCANASE, CHITINASE AND POLYPHENOLOXIDASE ACTIVITIES IN CACAO PODS UPON Phytophthora megakarya INOCULATION

Cacao (Theobroma cacao   L.) clones that differ in susceptibility to black pod disease were analysed for response to stress induced by pod inoculation with the fungus Phytophthora megakarya   Braz. Et Griff. Fungal inoculation significantly stimulated β-1,3-glucanase activity in both soluble and ionically-bound fractions of the less susceptible clones. No significant correlation was found in the other clones. Chitinase activity in both soluble and ionically-bound fractions was generally reduced upon pod inoculation with the fungus, but this pattern did not correlate with disease severity. Polyphenoloxidase activity, following pod inoculation, was genotype dependent in the soluble fractions, whereas in the ionically-bound fractions, stimulation of this activity was recorded in the less susceptible clones. Moreover, pod inoculation was characterised by the appearance of a new polyphenoloxidase isoform A'2 in the less susceptible clones

Role of root border cells in Cocoyam / P. myriotylum interaction

International audienc

Variation of β-1,3-Glucanase, Chitinase and Polyphenoloxidase Activities in Cacao Pods upon Phytophthora megakarya Inoculation

Cacao (Theobroma cacao L.) clones that differ in susceptibility to black pod disease were analysed for response to stress induced by pod inoculation with the fungus Phytophthora megakarya Braz. Et Griff. Fungal inoculation significantly stimulated β-1,3-glucanase activity in both soluble and ionically-bound fractions of the less susceptible clones. No significant correlation was found in the other clones. Chitinase activity in both soluble and ionically-bound fractions was generally reduced upon pod inoculation with the fungus, but this pattern did not correlate with disease severity. Polyphenoloxidase activity, following pod inoculation, was genotype dependent in the soluble fractions, whereas in the ionically-bound fractions, stimulation of this activity was recorded in the less susceptible clones. Moreover, pod inoculation was characterised by the appearance of a new polyphenoloxidase isoform A\'2 in the less susceptible clones. Key Words: Absorbance, cortex, ionically-bound, Theobroma cacao, wonding Résumé Les réponses aux stress induits par innoculation de gousses de cacao (Theobroma cacao L.), aux susceptibilités differentes à la maladie de Blackpod, par le Phytophthora megakarya Braz étaient analysées. L\'inoculation de fungi a significativement stimulé les activités de « glucanase » β-1,3 dans les deux fractions solubles et à liaison ionique des clones moins susceptibles. Pas des corrélations significatives étaient observées dans d\'autres clones. L\'activité de la chitanase dans les deux milieux était generalement reduite juste après l\'inoculation par le fongi, mais cette tendance n\'a pas corrélée avec la sévérité de la maladie. L\'activité du polyphenoloxidase, après inoculation de gousses, était généralement dependante du génotype dans la fraction soluble, alors que la stimulation de cette activité était observée dans les clones moins susceptibles. En plus, l\'inoculation des gousses était caracterisée par l\'apparition de nouveau polyphenolosidase isoformes A\'2 dans les clones les moins susceptibles. Mots Clés: Absorbance, cortex, ionically-bound, Theobroma cacao, wonding (Af Crop Sci J 2003 Vol 11 No 2 pp.97-106